(57) A powder coating composition comprises by weight (1) 100 parts of an epoxy resin (e.g. bisphenol A type),

(2) a hardener (e.g. an aromatic diamine),

(3) as filler (i) 30-180 parts of needle-like glass powder of average length at least 40 µm, preferably 50-350 µm, ratio of length: diameter at least 4:1, preferably 5:1 to 100:1, and average diameter 1-30 µm, preferably surface treated with a silane coupling agent and (ii) 30-150 parts of a granular inorganic filler (e.g. Ti0₂, BaS_O3) of average diameter 1.0 µm or less and preferably surface treated to increase its weltability; and

(4) 0.1-5.0 parts of an aminosilane, epoxysilane or mercaptosilane as coupling agent. The composition can be made by melt mixing and powdering.

A steel member, e.g. for a vehicle, is treated with a solution of phosphate, chromate or chromium/phosphoric acid to form a surface layer on which is deposited the powder which is heated to form a hardened coating having high impact resistance at ordinary and low temperature and forming an excellent protection against corrosion of the steel.